Document Detail


Asymmetrical response of the intraluminal and extraluminal surfaces of the porcine retinal artery to exogenous adenosine.
MedLine Citation:
PMID:  8994359     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The relative effects of exogenous adenosine applied intraluminally or extraluminally were compared on first-order pig retinal arteries in an isolated perfused artery preparation. First-order retinal arteries with at least one side branch were cannulated and perfused at a constant flow in an environmentally-controlled organ bath on the stage of an inverted microscope. Vessels were precontracted with 10(-4) methoxamine applied extraluminally, which produced a sustained contraction. Then, either extraluminal or intraluminal adenosine was added in increasing concentrations from 10(-9) to 10(-3) M. During these procedures continuous measurements of external vessel diameter were made. The average external diameter of the retinal arterial segments used was 127.6 +/- 2.3 microns (n = 13). Extraluminal methoxamine (10(-4) M) constricted the vessels to 77.9 +/- 2.0% (n = 9) and 78.8 +/- 0.8% (n = 4) of the control value for the vessels later exposed to extraluminal and intraluminal adenosine respectively. Extraluminal adenosine caused a dose-dependent dilatation which commenced between 10(-7) M and 10(-6) M, and reached a percentage dilatation of 22.6 +/- 1.8% (n = 9) at 10(-3) M. For concentrations of 10(-4) M and above, spontaneous oscillations in diameter were observed for extraluminally-applied adenosine with an average period of 0.46 +/- 0.02 (n = 9) cycles per minute. The average percentage diameter oscillation was +/- 7.1% of the mean diameter. In contrast, intraluminal adenosine failed to cause dilatation or spontaneous oscillations at all concentration values, although the dilatory ability of these vessels was confirmed by intraluminal application of the Ca2+ channel blocker verapamil. In conclusion this study has demonstrated that the two sides of the retinal artery wall are differentially sensitive to adenosine, with the intraluminal route being ineffective. In vivo, in hypoxic or ischemic situations, adenosine is released by extraluminal neural tissue and minimizes tissue damage, partially by acting as a signaller of metabolic status to the vasculature leading to vasodilatation and hence increased local blood flow. This study shows that delivery of adenosine for therapeutic purposes through an intraluminal route is not a feasible proposition. This isolated, perfused artery technique has considerable potential to improve our understanding of uptake mechanisms, metabolism and vasoactivity of the retinal vessel wall.
Authors:
V A Alder; E N Su; D Y Yu; S J Cringle; P K Yu
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Publication Detail:
Type:  In Vitro; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Experimental eye research     Volume:  63     ISSN:  0014-4835     ISO Abbreviation:  Exp. Eye Res.     Publication Date:  1996 Nov 
Date Detail:
Created Date:  1997-01-30     Completed Date:  1997-01-30     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0370707     Medline TA:  Exp Eye Res     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  557-64     Citation Subset:  IM    
Affiliation:
Lions Eye Institute, University of Western Australia, Nedlands, Australia.
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MeSH Terms
Descriptor/Qualifier:
Adenosine / administration & dosage,  pharmacology*
Animals
Arterioles / drug effects,  physiology
Culture Techniques
Dose-Response Relationship, Drug
Endothelium, Vascular / drug effects
Methoxamine / pharmacology
Muscle, Smooth, Vascular / drug effects
Retinal Artery / drug effects*,  physiology
Swine
Vasoconstriction / drug effects
Vasodilation / drug effects
Chemical
Reg. No./Substance:
390-28-3/Methoxamine; 58-61-7/Adenosine

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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